Four Quadrant Gates

In many railroad crossing applications such as quiet zones and high speed rail, four quadrant gates provide the most effective crossing protection. And when four quadrant gates are used, it makes sense to operate them is what the railroad industry calls dynamic mode. This is where the exit gates descend only when a vehicle detection system can confirm that there are no vehicles in the crossing island that would be trapped when all four gates are in the lowered position.

Until now, railroads had to rely on buried inductive loops to detect vehicles. While loops generally work satisfactorily, they are subjected to installation and operating environment traumas that limit their useful life. Once temperature-induced pavement heaving and continuous wheel compression distort the loop shape, they are useless. The crossing roadway must be excavated and the loops replaced to restore the crossing’s full functionality – a process that can take weeks, sometimes months.

Radar devices have been successfully deployed for years along highways and at signalized traffic intersections. Island Radar Company and traffic radar leader Wavetronix have developed the ideal solution for vehicle detection at crossings – the Island Radar.

Powered by the Wavetronix SmartSensor-Matrix technology and adapted for railroad use by Island Radar Company, the system provides 100% redundant vehicle detection with none of the consequences of presence detector loops. Viewing the crossing island from atop the exit or entrance gate masts, this dual radar system doesn’t miss anything. The Island Radar VDR24 controller, typically mounted in the crossing bungalow provides AREMA-compliant interface to virtually any type or vintage of crossing control circuitry.

With many times the life of typical buried loops and an installation time that is measured in hours rather than weeks, the Island Radar features half the life cycle cost of buried loops systems. Already at work on BNSF and Norfolk Southern crossings, the Island Radar is proving to be the smarter, more reliable choice for vehicle detection in four-quadrant gate crossing warning systems.

See the Island Radar in action:

In this recorded video you can watch live traffic move over the crossing island. The radar on the left side exit gate mast casts a 16,000 square foot detection footprint (in yellow) that is quarter-circle shaped, 90 degrees by 140 feet. Within that footprint two green detection zones have been established, one for each lane of traffic across the crossing island. As traffic moves through these detection zones you can see how the radar tracks, classifies, and detects the vehicles in both lanes, toggling the corresponding output channel connected to the crossing controller.